Yeah, the Tribesman thing is a really superficial note. I think it's one of those things that the way you used it doesn't feel like an inherently bad thing, but I do think that there are probably some people who would want to fix it in their games, where the Cultist/Worshipper angle doesn't have the same level of baggage.
I'm not familiar enough with Shadowdark to get a feel for how it would affect the balance of the adventure, but I wonder if you could adjust the time to shift on a 1-2. Then combine encounters 3-5 into two encounters. One where you see 1d6 Explorers take on 1d4 Tribesmen and another where you see 1d4 Explorers take on 1d6 Tribesman. I think that may help the dungeon feel like a dynamic place where things are happening. It may reduce some opportunities to have non-combat encounters, but I would think that the party could always just sit back and wait to talk to the winners.
Then you're looking at having more frequent time shifts but also the potential combat encounters have some dynamic decisions to make: side with the more powerful group, side with a group that you've already interacted with, side with a group you haven't interacted with, sit back and wait for the fight to be over, try to stop the fight and broker peace, etc.
Just some thoughts. In my mind, this is already a 5 star module, so anything I'm suggesting is a minor, cherry-on-top type of suggestion.